Apparatus for method for determining the degree of elongation of metal strips

ABSTRACT

An apparatus to perform the method which comprises the steps of forcibly applying vibrations to a metal strip to generate standing wave vibrations at a prescribed wavelength, and measuring the amplitude of the standing wave vibration, thereby defining the degree of elongation of said strip from the values of the amplitude and the wavelength.

United States Patent lnventors Morltada Kubo Tokyo; Kunijl Asano,Kawasaki-shi, both of, Japan Appl. No. 840,810 Filed July 10, 1969Patented July 13, 1971 Assignee Tokyo Shibaura Electric Co. Ltd.Kawasaki-shi, Japan Priority July 12, 1968 Japan 43/48458 APPARATUS FORMETHOD FOR DETERMINING THE DEGREE OF ELONGATION OF METAL STRIPS PrimaryExaminer-Richard C. Queisser Assistant ExaminerArthur E. KorkeszAttorney-Irving M. Weiner ABSTRACT: An apparatus to perform the methodwhich 6 Claims 7 Drawing Figs comprises the steps of forcibly applyingvibrations to a metal US. Cl. 73/67 strip to generate standing wavevibrations at a prescribed Int. Cl GOln 24/00 wavelength, and measuringthe amplitude of the standing Field of Search ..73/67, 67.2, wavevibration, thereby defining the degree of elongation of p 5 17 AV saidstrip from the values of the amplitude and the wavelength.

GAUGE 3 5% 8 4 HEP? Q {6 r .13 5 COMPUTING CIRCUIT T PATENIED JUL 1 aIBYI SHEET 1 [IF 2 FIG.

COMPUTING C I RCU IT SQUARE-LAW C I RCU I T APPARATUS FOR METHOD FORDETERMINING THE DEGREE F ELONGATION OF METAL STRIPS elongated uniformly.Local variations in the degree of elongation will lead to the occurrenceof undulations on the surface of a rolled metal strip. These undulationsmay broadly be classifted into those appearing along the central part ofthe strip extending in a direction perpendicular to the transversedirection of the strip, i.e., the direction in which it is rolled(hereinafter referred to as the central undulations") and thosepresented on the edge or edges of the strip (hereinafter referred to asthe edge undulations).

To prevent the occurrence of central or edge undulations, there are useda pair of crown rolls in rolling metal strips. The term crown roll", asused herein, denotes the type, the central portion of which generallyprojects outward, as well as a simple cylindrical type. To avoid thegeneration of edge undulations, the crown roll is designed to receive anexternal load to be so curved as to allow a greater pressure to beapplied to the central part of a rolled strip, and to eliminate theappearance of central undulations, said roll also receives such anexternal load to be so curved as to allow a greater pressure to beapplied to the edge portion of a rolled strip. Accordingly, theoccurrence of edge or central undulations can be restricted according tothe manner in which the external load is impressed. To control theapplication of said load, namely, the operation of the crown roll, it isnecessary to measure in advance the degree of deformation of a rolledstrip. However, such measurement presents considerable difficulties forthe following two reasons. First, the strip travels at a high speed, sothat a measuring method involving a mechanical contact with the surfaceof a strip is impracticable. Secondly, a metal strip is subject to afairly great tensile force at the time of rolling, so that the amplitudeof the wave form of edge and central undulations is smaller than whenthe strip is relieved of such tensile force.

It is accordingly the object of the present invention to provide anapparatus for determining the degree of elongation of a rolled metalstrip without directly contacting it.

In brief, the present invention consists in forcibly applying at theoutlet of work rolls vibrations like those having a standing wave of aprescribed wavelength to a travelling metal strip and measuring theamplitude of these vibrations without touching the strip, therebydefining the degree of its elongation.

This invention can be more fully understood from the following detaileddescription when taken in connection with reference to the accompanyingdrawings, in which:

FIGS. 1A and 1B are schematic perspective views of the typical examplesof the deformation of a rolled metal strip;

FIG. 2 is a diagrammatic represention of an apparatus according to anembodiment of the present invention;

FIG. 3 is an enlarged diagram of the main part of the embodiment of FIG.2;

FIG. 4 is a schematic diagram of a means for detecting the amplitude ofvibrations as employed in the embodiment of FIG. 2;

FIG. 5 is a block diagram showing a circuit for determining the degreeof elongation; and

FIG. 6 is a schematic diagram of an apparatus according to anotherembodiment of the invention.

Before describing an embodiment of the present invention, let us referto FIG. I in which the aforesaid central and edge undulations of thestrip 1 are denoted by 1a and 1b respectively.

There will now be described an embodiment of the present invention byreference to FIGS. 2 to 4, in which the same parts are denoted by thesame numerals. Referring to FIG. 2, a

metal strip 1 is rolled by a pair of work rolls 2 supported by a pair ofbackup rolls 3, and wound about a takeup reel 5 in the direction of anarrow by the medium of a guide roll 4. Between the work rolls 2 andguide roll 4 are disposed two pair of keep rolls 6 and 7 at a prescribedspace L. These keep rolls 6 and 7 so act as to restrict the scope of thevibrations of the strip 1 occuring in the direction of its thickness.

Numeral 8 represents vibration means disposed on the opposite sides ofthe strip 1. These vibration means 8 are operated by turns to vibratethe strip 1 at a prescribed frequency in the direction of the arrow 9 soas to forcibly generate vibration waves like standing waves (hereinafterreferring to as the standing wave"). The vibration means 8 may consistof those which eject, for example, the fluid to the strip 1 by turns, orthose which alternately apply an electromagnetic force to the strip 1 ifit is made of a magnetizable material, and can be easily prepared by theknown techniques. Numeral 11 is a detector for detecting the amplitude Aof the standing wave 10. Numeral 12 is a guage for measuring thedistance between the aforesaid two pairs of keep rolls 6 and 7, whichmay be formed of a potentiometer interlocking with, for example, saidkeep rolls 6 and 7. Signals representing the measured distance L andthose issued from the detector 11 are conducted to a circuit 13 forcomputing the degree of elongation of a metal strip. Numeral 14 denotessignals fed back to a means involved in a roll apparatus for controllingthe flatness of a strip known to those skilled in the art which isformed of a screwdown control device, crown control device and etc.

The foregoing description including the related drawing relates by wayof convenience to the case where a single detector 11 was employed.Generally, however, there are arranged a plurality of detectors in thetransverse direction of a metal strip, and also a plurality ofcalculation circuits 14 in corresponding relationship thereto.

There will now be described the operation of the apparatus of thepresent invention and the principle of determining the degree ofelongation of a rolled metal strip. When the strip travels quickly,vibrations occurring in the direction of its thickness present acomplicated state in which vibrations having progressive waves likethose presented by edge and central undulations resulting from therolling of said strip overlap the intrinsic vibrations defined by thetensile force acting on the strip 1 and the interval between the keeprolls 6 and 7. Of these vibrations, those represented by the edge andcentral undulations are the so-called buckling phenomenon, so that whena metal strip travels quickly, they irregular vary in wavelength andphase and present complicated waveforms. However, if vibrations areforcibly applied, as in the method of the present invention, to a metalstrip held by keep means disposed at a prescribed space L, there can beobtained a standing wave in which the half wavelength is equal to L andthe function of waveforms is substantially fixed. Accordingly,determination of the amplitude of said standing wave enables the degreeof elongation of those parts of a strip corresponding to the standingwave to be easily computed.

Referring to FIG. 3, the longitudinal direction of the strip 1 isdesignated as an x axis, the direction thereof perpendicular to saidlongitudinal direction and extending toward the vibration means 8 as a yaxis and the point at which the x and y axes intersect each other as thebase point 0. Then the standing wave 10 having a maximum amplitude A maybe approximately expressed by equation I below.

y==A sin 1r/L-x I (In this case, the amplitude A is far smaller than thehalf wavelength L, so that approximation using a sine wave does notpractically present any difficulties.) The length L of that portion of ametal strip in which there are generated standing waves whose amplitudeis A and whose half wavelength is L may be expressed by equation llbelow With the distance L between the keep means or rolls taken as thebase, the degree e of elongation of a metal strip may be determined fromequation lll below.

This degree e of elongation can be calculated immediately by thecomputation circuit 13. For example, the circuit 13 for determining thedegree of elongation e as shown in FIG. 5 comprises a ratio circuitwhich is impressed with the output voltage V (V =K, -L where K denotesthe constant of a unit volt/cm.) of the gauge for distance and theoutput voltage V (V =K -A where K, denoted the constant of a unitvolt/cm.) of the detector 111 and gives forth an output corresponding tothe ratio between these input voltages (V /V and a squarelaw circuitwhich is cascade connected to the first mentioned circuit to squareoutputs therefrom. If the degree e of elongation is determined at aplurality of points located in the transverse direction of a metalstrip, and a load to be applied to a means for controlling the flatnessof the surface of the metal strip, for example, a pair of crown rolls,are adjusted in accordance with the distribution pattern of thedetermined degrees of elongation at said points thereby to cause saidrolls to be curved in a desired manner, then it will be possible tocontrol the shape or flatness of the rolled metal strip.

The amplitude A of the standing wave can be detected, for example,optically. There will now be described an example of such detection byreference to FIG. 4. in this figure, the travelling direction of a metalstrip 1 is designated as an x axis, the direction of its thickness as ay axis, its transverse direction as z axis and the point at which thethree axes intersect each other as the base point 0. The standing wavecut by the x -y plane is indicated by the aforementioned equation l. Nowlet it be assumed that light beams 15 are projected from point P( X, H,a) to point R(X, O, 0). Then the reflected light beams 15' will displaydifferent distances id from point Q(X, H, a). ln case of H A, saiddistance d may be expressed as follows:

If, the distance d is determined as a difference in the amounts oflightbeams detected by a pair of photoelectric detectors S and 8 divided bythe y-z plane with x taken as equal to X, then the amplitude A of therelated standing wave can be easily defined from equation lV above.

The standing wave may be generated, as illustrated in FIG. 6, byarranging two rolls to and 16 acting as guide rolls at an interval of Linstead of using the aforementioned keep rolls 6 and 7. Further the workrolls 2 may be substituted for-one of said rolls l6 and 116'. lt willalso be apparent that means for generating the standing wave and meansfor determining the amplitude thereof are not limited to those used inthe aforementioned embodiments.

What we claim is:

1. An apparatus for determining the degree of elongation of metal stripsbefore they are wound about a takeup device after they are rolled bywork rolls which comprises means for forcibly applying between the workrolls and takeup device vibrations having a prescribed frequency to atravelling metal strip in the direction of its thickness, means forlimiting the scope of vibrations generated by said vibration means tothe prescribed portion of the metal strip in its longitudinal direction,so as to cause vibrations substantially to display a standing wavehaving a prescribed wavelength, means for determining the amplitude ofthe standing wave vibrations in the metal strip, and means for computingthe degree of elongation of the metal strip upon receipt of signalsrepresenting said amplitude issued from the amplitude determining means.

2. An apparatus according to claim 1 wherein the means for forciblyapplying vibrations consists of a pair of ejecting devices disposed onthe opposite sides of the metal strip in a manner to face each other andso designed as to eject fluid by turns to the metal strip.

3. An apparatus according to claim 1 wherein the means for forciblyapplying vibrations consists of a pair of electromagnetic devicespositioned on the opposite sides of the metal strip in a manner to faceeach other and so designed as to apply an electromagnetic force to themetal strip.

4. An apparatus according to claim 1 wherein the means for limiting thescope of vibrations consists of two pairs of rolls arranged at aprescribed interval in a manner to hold the metal strip therebetween.

5. An apparatus according to claim 1 wherein said amplitude determiningmeans comprises a plurality of detectors in the transverse direction ofthe strip.

6. An apparatus according to claim 1 wherein said amplitude determiningmeans consists of a light source to project light beams to the strip anda pair of photoelectric converters arranged to receive the light beamsreflected from said strip to generate an electrical signal.

2. An apparatus according to claim 1 wherein the means for forciblyapplying vibrations consists of a pair of ejecting devices disposed onthe opposite sides of the metal strip in a manner to face each other andso designed as to eject fluid by turns to the metal strip.
 3. Anapparatus according to claim 1 wherein the means for forcibly applyingvibrations consists of a pair of electromagnetic devices positioned onthe opposite sides of the metal strip in a manner to face each other andso designed as to apply an electromagnetic force to the metal strip. 4.An apparatus according to claim 1 wherein the means for limiting thescope of vibrations consists of two pairs of rolls arranged at aprescribed interval in a manner to hold the metal strip therebetween. 5.An apparatus according to claim 1 wherein said amplitude determiningmeans comprises a plurality of detectors in the transverse direction ofthe strip.
 6. An apparatus according to claim 1 wherein said amplitudedetermining means consists of a light source to project light beams tothe strip and a pair of photoelectric converters arranged to receive thelight beams reflected from said strip to generate an electrical signal.